1. Field of the Invention
The present invention generally relates to an image forming apparatus using an electrophotographic method, a cartridge mountable on this image forming apparatus main body, that is, a process cartridge, a development apparatus rendered as a cartridge, an image forming system, and a storage medium mounted on the cartridge.
Here, the electrophotographic image forming apparatuses include an electrophotographic copier, an electrophotographic printer (such as an LED printer and a laser beam printer), and an electrophotographic facsimile, for instance.
In addition, a cartridge removable from the electrophotographic image forming apparatus refers to the cartridge having at least one of an electrophotographic photosensitive body, charging means for charging the electrophotographic photosensitive body, developing means for supplying developer to the electrophotographic photosensitive body, and cleaning means for cleaning the electrophotographic photosensitive body. In particular, the process cartridge refers to either the cartridge integrating into a cartridge at least one of the charging, development and cleaning means and the electrophotographic photosensitive body and rendering it removable from the electrophotographic image forming apparatus main body, or the cartridge integrating into a cartridge at least the developing means and the electrophotographic photosensitive body and rendering it removable from the apparatus main body.
2. Related Art
Conventionally, in an image forming apparatus using an electrophotographic image forming process, a process cartridge method of integrating into a cartridge an electrophotographic photosensitive body and process means for acting upon the element and rendering it removable from the image forming apparatus main body is adopted. This process cartridge method allows a user to perform maintenance of the apparatus on his or her own without relying on a serviceperson, so that operability can be exceptionally improved. For this reason, the process cartridge method is widely used in the electrophotographic image forming apparatuses.
A method of mounting a memory as storage means on the process cartridge (hereafter, merely referred to as a “cartridge”) to store information of the cartridge is also disclosed. For instance, Japanese Patent Application Laid-Open No. 10-221938 proposes to store in memory manufacturing lots, types, developer (toner) types and so on of the cartridges so as to perform quality control of the cartridges.
In addition, there is a proposed method of stabilizing image quality regardless of situation of use by mounting a memory on the cartridge. U.S. Pat. No. 5,272,503 discloses an image forming apparatus for recording in memory at any time the number of printed (duplicated) sheets totalized as an amount of the cartridge used in the apparatus main body and controlling process conditions according to a totalized value of the number of printed sheets. However, in the case where the used amount of a photosensitive drum that is the electrophotographic photosensitive body is rendered as the totalized value of the number of printed sheets as the above-mentioned used amount of the cartridge, there is a defect that its precision is not good. This is because, for instance, A3-sized sheet is counted as one sheet that is the same as A4-sized sheet.
Moreover, there is also a method of directly detecting the used amount of the photosensitive drum from a lowered charged potential of the drum or a reduced latent image contrast by using a surface potential sensor or the like. In this case, however, the surface potential sensor and an electric circuit for processing its output are required, and so the costs become high. In addition, as only the information on the photosensitive drum corresponding to the sensor's position is acquired, there is a possibility of detecting a partial defect, not necessarily capable of acquiring the information along the whole length of the drum.
Furthermore, even if the precise used amount of the cartridge is known, there are cases where it is difficult to render images uniform throughout the usage period of the cartridge. This is because there are some differences in variations in images against the used amount of the cartridge due to manufacturing conditions thereof and so on, and the differences in the images become obvious from the middle to the latter half of the usage period.
As an example of this case, a relationship between the drum's film thickness and a light portion potential VI is shown in FIG. 10. As is understandable from this graph, the light portion potential of the drum has dependence on the film thickness.
Thus, as the cartridge is used for a long period of time, the drum's film thickness is reduced so that the light portion potential changes and the quality of formed images vary. However, a reduced amount of the film thickness varied at times depending on the conditions on manufacturing of the cartridges even though the used amount was the same.
This variation in the reduced amount of the film thickness of the drum is generated by manufacturing variation in contact pressure at a cleaning blade of the cartridge, variation in electric characteristics of the charging means and so on, for instance.